/Engine/Source/Runtime/Engine/Classes/Materials/MaterialExpressionMaterialFunctionCall.h
Set a new material function, given an old function so that links can be passed over if the name matches.
true if setting the function was a success, false if it failed.
bool SetMaterialFunctionEx ( [UMaterialFunctionInterface](API\Runtime\Engine\Materials\UMaterialFunctionInterface) * OldFunctionResource, [UMaterialFunctionInterface](API\Runtime\Engine\Materials\UMaterialFunctionInterface) * NewResource )